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13 lines
911 B
Markdown
13 lines
911 B
Markdown
---
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title: 'How to speed up LZ4 decompression in ClickHouse?'
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image: 'https://blog-images.clickhouse.com/en/2019/how-to-speed-up-lz4-decompression-in-clickhouse/main.jpg'
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date: '2019-06-25'
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tags: ['performance', 'lz4', 'article', 'decompression']
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---
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When you run queries in [ClickHouse](https://clickhouse.com/), you might notice that the profiler often shows the `LZ_decompress_fast` function near the top. What is going on? This question had us wondering how to choose the best compression algorithm.
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ClickHouse stores data in compressed form. When running queries, ClickHouse tries to do as little as possible, in order to conserve CPU resources. In many cases, all the potentially time-consuming computations are already well optimized, plus the user wrote a well thought-out query. Then all that's left to do is to perform decompression.
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[Read further](https://habr.com/en/company/yandex/blog/457612/)
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